15-year survivorship analysis of an interspinous device in surgery for single-level lumbar disc herniation

Background Interspinous devices have been introduced as alternatives to decompression or fusion in surgery for degenerative lumbar diseases. This study aimed to investigate 15-year survivorship and risk factors for reoperation of a Device for Intervertebral Assisted Motion (DIAM) in surgery for 1-level lumbar disc herniation (LDH). Methods A total of 94 patients (54 men and 40 women) underwent discectomy and DIAM implantation for 1-level LDH, with a mean follow-up of 12.9 years (range, 6.3–15.3 years). The mean age was 46.2 years (range, 21–65 years). Sixty-two patients underwent DIAM implantation for L4–5, 27 for L5–6, and 5 for L3–4. Reoperations due to any reason associated with DIAM implantation level or adjacent levels were defined as failure and used as the end point of determining survivorship. Results During the 15-year follow-up, 8 patients (4 men and 4 women) underwent reoperation due to recurrence of LDH at the DIAM implantation level, a reoperation rate of 8.5%. The mean time to reoperation was 6.5 years (range, 0.8–13.9 years). Kaplan-Meier analysis showed a cumulative survival rate of the DIAM implantation of 97% at 5 years, 93% at 10 years, and 92% at 15 years after surgery; the cumulative reoperation rate of the DIAM implantation was 3% at 5 years, 7% at 10 years, and 8% at 15 years after surgery. Mean survival time was predicted to be 14.5 years (95% CI, 13.97–15.07). The log-rank test and Cox proportional hazard model showed that age, sex, and location did not significantly affect the reoperation rate of DIAM implantation. Conclusions Our results showed that DIAM implantation significantly decreased reoperation rate for LDH in the 15-year survivorship analysis. We suggest that DIAM implantation could be considered a useful intermediate step procedure for LDH surgery. To the best of our knowledge, this is the longest follow-up study in which surgical outcomes of interspinous device surgery were reported.

Functional and radiographic evaluation of an interspinous device as an adjunct for lumbar interbody fusion procedures

In the last decades, several interspinous process devices were designed as a minimally invasive treatment option for spinal stenosis. In order to minimise surgical trauma, interspinous process devices were recently discussed as an alternative posterior fixation in vertebral interbody fusions. Therefore, the purpose of this study was to evaluate the effect of a newly designed interspinous device with polyester bands (PBs) on range of motion (RoM) and centre of rotation (CoR) of a treated motion segment in comparison with an established interspinous device with spikes (SC) as well as with pedicle screw instrumentation in lumbar fusion procedures. Flexibility tests with an applied pure moment load of 7.5 Nm were performed in six monosegmental thoracolumbar functional spinal units (FSUs) in the following states: (a) native, (b) native with PB device, (c) intervertebral cage with PB device, (d) cage with SC and (e) cage with internal fixator. The resulting RoM was normalised to the native RoM. The CoR was determined of X-ray images taken in maximal flexion and extension during testing. In flexion and extension, the PB device without and with the cage reduced the RoM of the native state to 58% [standard deviation (SD) 17.8] and 53% (SD 15.7), respectively. The SC device further reduced the RoM to 27% (SD 16.8), while the pedicle screw instrumentation had the most reducing effect to 17% (SD 17.2) (p < 0.01). In lateral bending and axial rotation, the interspinous devices had the least effect on the RoM. Compared to the native state, for all instrumentations the CoR showed a small shift towards cranial. In the anterior-posterior direction, the SC device and the pedicle screw instrumentation shifted the CoR towards the posterior wall. The interspinous devices significantly reduced the RoM in flexion/extension, while in axial rotation and lateral bending only the internal fixator had a significant effect on the RoM.

Long-term Results for the BacJac Interspinous Device in Lumbar Spine Degenerative Disease

Objective To evaluate the long-term results of using the BacJac interspinous device (Pioneer Surgical Technology Inc.) in a series of patients with degenerative lumbar spine disease. Methods Forty-one patients undergoing lumbar surgery with implantation of a BacJac device from 2009 to 2012 were enrolled in the present study. Patients were evaluated using the Oswestry Disability Scale (ODI). Results Although all patients showed a significant improvement of the ODI score immediately after surgery, only 41% of patients showed a satisfactory outcome. We observed worse results in the patients operated on at the L3–L4 level and in whom the device was implanted in a segment different from the one where surgical decompression had been performed. Weight gain in the months after surgery was also a poor outcome-influencing factor. Conclusions This study confirms what is already suggested in the relevant literature regarding the long-term inefficacy of the so-called dynamic stabilization devices.

Biomechanical effects of hybrid stabilization on the risk of proximal adjacent-segment degeneration following lumbar spinal fusion using an interspinous device or a pedicle screw–based dynamic fixator

OBJECTIVEPedicle screw-rod–based hybrid stabilization (PH) and interspinous device–based hybrid stabilization (IH) have been proposed to prevent adjacent-segment degeneration (ASD) and their effectiveness has been reported. However, a comparative study based on sound biomechanical proof has not yet been reported. The aim of this study was to compare the biomechanical effects of IH and PH on the transition and adjacent segments.METHODSA validated finite element model of the normal lumbosacral spine was used. Based on the normal model, a rigid fusion model was immobilized at the L4–5 level by a rigid fixator. The DIAM or NFlex model was added on the L3–4 segment of the fusion model to construct the IH and PH models, respectively. The developed models simulated 4 different loading directions using the hybrid loading protocol.RESULTSCompared with the intact case, fusion on L4–5 produced 18.8%, 9.3%, 11.7%, and 13.7% increments in motion at L3–4 under flexion, extension, lateral bending, and axial rotation, respectively. Additional instrumentation at L3–4 (transition segment) in hybrid models reduced motion changes at this level. The IH model showed 8.4%, −33.9%, 6.9%, and 2.0% change in motion at the segment, whereas the PH model showed −30.4%, −26.7%, −23.0%, and 12.9%. At L2–3 (adjacent segment), the PH model showed 14.3%, 3.4%, 15.0%, and 0.8% of motion increment compared with the motion in the IH model. Both hybrid models showed decreased intradiscal pressure (IDP) at the transition segment compared with the fusion model, but the pressure at L2–3 (adjacent segment) increased in all loading directions except under extension.CONCLUSIONSBoth IH and PH models limited excessive motion and IDP at the transition segment compared with the fusion model. At the segment adjacent to the transition level, PH induced higher stress than IH model. Such differences may eventually influence the likelihood of ASD.